The Bristol Neptune was a seven-cylinder air-cooled radial engine developed in 1930. It had the same size cylinders as the earlier Mercury and Titan engines, 5.75 in (146 mm) x 6.5 in (165 mm) which gave a displacement of 1,182 cu in (19.3 L) and produced a maximum of 320 horsepower (239 kW). The Neptune was effectively a seven-cylinder version of the Titan.
Bristol Type 110
Type: 7-cylinder air-cooled radial engine.
Bore: 5.75 in (146 mm)
Stroke: 6.5 in (165 mm)
Displacement: 1,182 cu in (19.3 L)
Diameter: 48.4 in (1229.3 mm)
Dry weight: 630 lb (286 kg)
Designer: Roy Fedden
Valvetrain: Overhead valve, Four valves per cylinder
Fuel type: 73-77 octane petrol
Cooling system: Air-cooled
Reduction gear: Direct drive, left hand tractor
Power output: 295 hp (220 kW) at 1,700 rpm (rated power), 320 hp (239 kW) at 1,870 rpm at sea level
Compression ratio: 5:1
Power-to-weight ratio: 0.5 hp/lb (0.83 kW/kg)